One `/model --global` produced four config.yaml shapes. CLI wrote
default/provider/base_url/api_mode and cleared the context pin on a route
change; the gateway rewrote the whole `model:` block (whole-file save_config)
and only set api_mode for `custom`; the TUI wrote three keys and never
touched api_mode, so a switch off an Anthropic-wire endpoint left a stale
`api_mode: anthropic_messages` in config; the dashboard main slot had its own
switched-provider logic, wrote `base_url: ""` and always dropped
context_length. ACP `session/set_model` and `POST /api/model/set` accepted
any model string (parse_model_input + detect_provider_for_model) so a model
no catalog knows, or a provider with no credentials, was handed to the
session / persisted and only failed at inference time.
Canonical: `hermes_cli.model_switch.model_selection_config_updates` (the
shape) + `persist_model_selection(result, config_path=None)` (targeted
per-key `atomic_roundtrip_yaml_update` writes, so sibling
`model_slots`/`model_fallback` keys survive; explicit path for the
multiplexed gateway's profile config) + `apply_model_selection` (same shape
applied to an in-memory `model:` dict for callers that save a whole
document). `atomic_roundtrip_yaml_update(value=None)` now REMOVES the key
instead of writing `key: null`, so per-key and whole-document writers land
the same file. Shape = CLI/gateway semantics: default, provider, base_url
(cleared when the target has none), api_mode (cleared when unresolved),
context_length cleared only when `should_clear_context_pin` says the route
identity changed, inline api_key/api cleared for non-custom targets.
Sites -> canonical:
hermes_cli/cli_model_switch_mixin.py::_persist_global_switch -> deleted; _commit_model_switch calls persist_model_selection
hermes_cli/cli_model_switch_mixin.py::_clear_persisted_context_for_model_switch -> deleted (folded into the shape)
gateway/slash_commands_model.py::_persist_model_switch_to_config -> to_thread forwarder: persist_model_selection(result, ctx.config_path)
tui_gateway/model_switch.py::_persist_model_switch -> deleted; _apply_model_switch calls persist_model_selection
hermes_cli/web_server_config.py::_apply_main_model_assignment -> apply_model_selection(result) (+ explicit custom api_key)
hermes_cli/web_server_config.py::_validated_main_model_selection -> NEW: switch_model(--provider) gate; rejection -> HTTP 400
hermes_cli/web_routers/{models,profiles,config_env}.py main-slot paths -> through _validated_main_model_selection
acp_adapter/server.py::_resolve_model_selection -> deleted; _switch_model calls switch_model (provider:model -> --provider), rejection -> ValueError
Behavior changes: TUI --global now writes/clears model.api_mode and clears a
route-changed context pin; gateway --global no longer rewrites the whole
model block (sibling keys survive) and clears api_mode for every target;
dashboard main slot / profile-create model / custom-endpoint activate now
reject unknown/uncredentialed/unlisted models (HTTP 400) and persist the
resolved base_url/api_mode instead of `base_url: ""`; ACP rejects the same
(ValueError surfaced by the command/protocol handler). Gateway persist runs
on a worker thread against the routed profile's config_path (multiplex-safe).
Cleared keys are removed from config.yaml rather than left as `null`. ACP
still never persists.
Kept `_normalize_main_model_assignment`: switch_model rejects a vendor name
posing as a provider (`moonshotai` -> "Unknown provider"), so the
vendor->aggregator repair is not a duplicate; E2E verified both branches.
No config migration: readers already coalesce `base_url: ""` to absent
(`_config_base_url_for_provider`) and gate api_mode on provider match
(`_provider_supports_explicit_api_mode`), so no stale-shape reader bug.
Tests: tests/hermes_cli/test_model_persist_one_shape.py (four surfaces land
one block; same-route re-pick keeps the pin), tests/acp_adapter/
test_acp_dashboard_model_switch_validation.py (rejection + explicit
provider prefix). Replaces test_acp_set_model_explicit_provider.py and the
two TUI-only persist tests; tests that intercepted the old per-surface seams
(`cli.save_config_value`, `load_config_readonly`, `tui_gateway.server.
_persist_model_switch`) now intercept the canonical seam. Each fix
sabotage-verified red.
cli_model_switch_mixin: the identical snapshot->stage->agent.switch_model->rollback
block in _apply_model_switch_result and _confirm_and_apply_cli_model_switch (2x47
lines) -> _stage_and_swap_model(result, old_model) -> bool. cli_loops_mixin: the
identical reversed-history assistant-text extraction in the loop-tick and goal
post-turn hooks -> _last_assistant_response_text(). Four _StubCLI test doubles bind
the new helper to the real implementation.
`_apply_model_switch_result` (the interactive `/model` picker's
confirmation path) printed `ModelInfo.context_window` straight from
models.dev, which reports the vendor-wide value (1.05M for gpt-5.5 on
openai). ChatGPT Codex OAuth caps the same slug at 272K, so the picker
showed 1M while the runtime (compressor, gateway `/model`, typed
`/model <name>`) correctly used 272K — the classic 'sometimes 1M,
sometimes 272K' mismatch on a single model.
Both display paths now go through `resolve_display_context_length()`,
matching the fix that `_handle_model_switch` received earlier.
Also bump the stale last-resort fallback in DEFAULT_CONTEXT_LENGTHS
(`gpt-5.5: 400000 -> 1050000`) to match the real OpenAI API value; the
272K Codex cap is already enforced via the Codex-OAuth branch, so the
fallback now reflects what every non-Codex probe-miss should see.
Tests: adds `test_apply_model_switch_result_context.py` with three
scenarios (Codex cap wins, OpenRouter shows 1.05M, resolver-empty falls
back to ModelInfo). Updates the existing non-Codex fallback test to
assert 1.05M (the correct value).
## Validation
| path | before | after |
|-------------------------------|-----------|-----------|
| picker -> gpt-5.5 on Codex | 1,050,000 | 272,000 |
| picker -> gpt-5.5 on OpenAI | 1,050,000 | 1,050,000 |
| picker -> gpt-5.5 on OpenRouter | 1,050,000 | 1,050,000 |
| typed /model gpt-5.5 on Codex | 272,000 | 272,000 |
teknium1